This example writes goal position of Dynamixels connected with two ports, and reads their present position until Dynamixels stop moving.

Available Dynamixel

All series using protocol 1.0

Sample code

#!/usr/bin/env python# -*- coding: utf-8 -*-## multi_port.py## Created on: 2016. 6. 16.# Author: Ryu Woon Jung (Leon)### ********* Multi Port Example *********### Available Dynamixel model on this example : All models using Protocol 1.0# This example is designed for using two Dynamixel MX-28, and two USB2DYNAMIXEL.# To use another Dynamixel model, such as X series, see their details in E-Manual(support.robotis.com) and edit below variables yourself.# Be sure that Dynamixel MX properties are already set as %% ID : 1 / Baudnum : 1 (Baudrate : 1000000 [1M])#importos,sysifos.name=='nt':importmsvcrtdefgetch():returnmsvcrt.getch().decode()else:importtty,termiosfd=sys.stdin.fileno()old_settings=termios.tcgetattr(fd)tty.setraw(sys.stdin.fileno())defgetch():returnsys.stdin.read(1)os.sys.path.append('../dynamixel_functions_py')# Path settingimportdynamixel_functionsasdynamixel# Uses Dynamixel SDK library# Control table addressADDR_MX_TORQUE_ENABLE=24# Control table address is different in Dynamixel modelADDR_MX_GOAL_POSITION=30ADDR_MX_PRESENT_POSITION=36# Protocol versionPROTOCOL_VERSION=1# See which protocol version is used in the Dynamixel# Default settingDXL1_ID=1# Dynamixel ID: 1DXL2_ID=2# Dynamixel ID: 2BAUDRATE=1000000DEVICENAME1="/dev/ttyUSB0".encode('utf-8')# Check which port is being used on your controllerDEVICENAME2="/dev/ttyUSB1".encode('utf-8')# ex) Windows: "COM1" Linux: "/dev/ttyUSB0"TORQUE_ENABLE=1# Value for enabling the torqueTORQUE_DISABLE=0# Value for disabling the torqueDXL_MINIMUM_POSITION_VALUE=100# Dynamixel will rotate between this valueDXL_MAXIMUM_POSITION_VALUE=4000# and this value (note that the Dynamixel would not move when the position value is out of movable range. Check e-manual about the range of the Dynamixel you use.)DXL_MOVING_STATUS_THRESHOLD=10# Dynamixel moving status thresholdESC_ASCII_VALUE=0x1bCOMM_SUCCESS=0# Communication Success result valueCOMM_TX_FAIL=-1001# Communication Tx Failed# Initialize PortHandler Structs# Set the port path# Get methods and members of PortHandlerLinux or PortHandlerWindowsport_num1=dynamixel.portHandler(DEVICENAME1)port_num2=dynamixel.portHandler(DEVICENAME2)# Initialize PacketHandler Structsdynamixel.packetHandler()index=0dxl_comm_result=COMM_TX_FAIL# Communication resultdxl_goal_position=[DXL_MINIMUM_POSITION_VALUE,DXL_MAXIMUM_POSITION_VALUE]# Goal positiondxl_error=0# Dynamixel errordxl1_present_position=0# Present positiondxl2_present_position=0# Open port1ifdynamixel.openPort(port_num1):print("Succeeded to open the port!")else:print("Failed to open the port!")print("Press any key to terminate...")getch()quit()# Open port2ifdynamixel.openPort(port_num2):print("Succeeded to open the port!")else:print("Failed to open the port!")print("Press any key to terminate...")getch()quit()# Set port1 baudrateifdynamixel.setBaudRate(port_num1,BAUDRATE):print("Succeeded to change the baudrate!")else:print("Failed to change the baudrate!")print("Press any key to terminate...")getch()quit()# Set port2 baudrateifdynamixel.setBaudRate(port_num2,BAUDRATE):print("Succeeded to change the baudrate!")else:print("Failed to change the baudrate!")print("Press any key to terminate...")getch()quit()# Enable Dynamixel#1 Torquedynamixel.write1ByteTxRx(port_num1,PROTOCOL_VERSION,DXL1_ID,ADDR_MX_TORQUE_ENABLE,TORQUE_ENABLE)ifdynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION))else:print("Dynamixel#1 has been successfully connected")# Enable Dynamixel#2 Torquedynamixel.write1ByteTxRx(port_num2,PROTOCOL_VERSION,DXL2_ID,ADDR_MX_TORQUE_ENABLE,TORQUE_ENABLE)ifdynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION))else:print("Dynamixel#2 has been successfully connected")while1:print("Press any key to continue! (or press ESC to quit!)")ifgetch()==chr(ESC_ASCII_VALUE):break# Write Dynamixel#1 goal positiondynamixel.write2ByteTxRx(port_num1,PROTOCOL_VERSION,DXL1_ID,ADDR_MX_GOAL_POSITION,dxl_goal_position[index])ifdynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION))# Write Dynamixel#2 goal positiondynamixel.write2ByteTxRx(port_num2,PROTOCOL_VERSION,DXL2_ID,ADDR_MX_GOAL_POSITION,dxl_goal_position[index])ifdynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION))while1:# Read present positiondxl1_present_position=dynamixel.read2ByteTxRx(port_num1,PROTOCOL_VERSION,DXL1_ID,ADDR_MX_PRESENT_POSITION)ifdynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION))# Read present positiondxl2_present_position=dynamixel.read2ByteTxRx(port_num2,PROTOCOL_VERSION,DXL2_ID,ADDR_MX_PRESENT_POSITION)ifdynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION))print("[ID:%03d] GoalPos:%03d PresPos:%03d\t[ID:%03d] GoalPos:%03d PresPos:%03d"%(DXL1_ID,dxl_goal_position[index],dxl1_present_position,DXL2_ID,dxl_goal_position[index],dxl2_present_position))ifnot((abs(dxl_goal_position[index]-dxl1_present_position)>DXL_MOVING_STATUS_THRESHOLD)or(abs(dxl_goal_position[index]-dxl2_present_position)>DXL_MOVING_STATUS_THRESHOLD)):break# Change goal positionifindex==0:index=1else:index=0# Disable Dynamixel#1 Torquedynamixel.write1ByteTxRx(port_num1,PROTOCOL_VERSION,DXL1_ID,ADDR_MX_TORQUE_ENABLE,TORQUE_DISABLE)ifdynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num1,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num1,PROTOCOL_VERSION))# Disable Dynamixel#2 Torquedynamixel.write1ByteTxRx(port_num2,PROTOCOL_VERSION,DXL2_ID,ADDR_MX_TORQUE_ENABLE,TORQUE_DISABLE)ifdynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION)!=COMM_SUCCESS:dynamixel.printTxRxResult(PROTOCOL_VERSION,dynamixel.getLastTxRxResult(port_num2,PROTOCOL_VERSION))elifdynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION)!=0:dynamixel.printRxPacketError(PROTOCOL_VERSION,dynamixel.getLastRxPacketError(port_num2,PROTOCOL_VERSION))# Close portdynamixel.closePort(port_num1)dynamixel.closePort(port_num2)

# Control table addressADDR_MX_TORQUE_ENABLE=24# Control table address is different in Dynamixel modelADDR_MX_GOAL_POSITION=30ADDR_MX_PRESENT_POSITION=36

Dynamixel series have their own control tables: Addresses and Byte Length in each items. To control one of the items, its address (and length if necessary) is required. Find your requirements in http://support.robotis.com/.

# Protocol versionPROTOCOL_VERSION=1# See which protocol version is used in the Dynamixel

Dynamixel uses either or both protocols: Protocol 1.0 and Protocol 2.0. Choose one of the Protocol which is appropriate in the Dynamixel.

# Default settingDXL1_ID=1# Dynamixel ID: 1DXL2_ID=2# Dynamixel ID: 2BAUDRATE=1000000DEVICENAME1="/dev/ttyUSB0".encode('utf-8')# Check which port is being used on your controllerDEVICENAME2="/dev/ttyUSB1".encode('utf-8')# ex) Windows: "COM1" Linux: "/dev/ttyUSB0"TORQUE_ENABLE=1# Value for enabling the torqueTORQUE_DISABLE=0# Value for disabling the torqueDXL_MINIMUM_POSITION_VALUE=100# Dynamixel will rotate between this valueDXL_MAXIMUM_POSITION_VALUE=4000# and this value (note that the Dynamixel would not move when the position value is out of movable range. Check e-manual about the range of the Dynamixel you use.)DXL_MOVING_STATUS_THRESHOLD=10# Dynamixel moving status thresholdESC_ASCII_VALUE=0x1b

Here we set some variables to let you freely change them and use them to run the example code.

As the document previously said in previous chapter, customize Dynamixel control table items, such as DXL_ID number, communication BAUDRATE, and the DEVICENAME, on your own terms of needs. In particular, BAUDRATE and DEVICENAME have systematical dependencies on your controller, so make clear what kind of communication method you will use.

The example uses two Dynamixels DXL1_ID, DXL2_ID connected with each ports DEVICENAME1, DEVICENAME2

Dynamixel basically needs the TORQUE_ENABLE to be rotating or give you its internal information. On the other hand, it doesn’t need torque enabled if you get your goal, so finally do TORQUE_DISABLE to prepare to the next sequence.

Since the Dynamixel has its own rotation range, it may shows malfunction if your request on your dynamixel is out of range. For example, Dynamixel MX-28 and Dynamixel PRO 54-200 has its rotatable range as 0 ~ 4028 and -250950 ~ 250950, each.

DXL_MOVING_STATUS_THRESHOLD acts as a criteria for verifying its rotation stopped.

Each of the variables above show the meaning of the communication result value.

# Initialize PortHandler Structs# Set the port path# Get methods and members of PortHandlerLinux or PortHandlerWindowsport_num1=dynamixel.portHandler(DEVICENAME1)port_num2=dynamixel.portHandler(DEVICENAME2)

portHandler() function sets port path as DEVICENAME1 and DEVICENAME2 and get port_num1 and port_num2 each, and prepares an appropriate functions for port control in controller OS automatically. port_num1 and port_num2 would be used in many functions in the body of the code to specify the port for use.

index variable points the direction to where the Dynamixel should be rotated.

dxl_comm_result indicates which error has been occurred during packet communication.

dxl_goal_position stores goal points of Dynamixel rotation.

dxl_error shows the internal error in Dynamixel.

dxl1_present_position and dxl2_present_position view where now each Dynamixel points out.

# Open port1ifdynamixel.openPort(port_num1):print("Succeeded to open the port!")else:print("Failed to open the port!")print("Press any key to terminate...")msvcrt.getch()quit()# Open port2ifdynamixel.openPort(port_num2):print("Succeeded to open the port!")else:print("Failed to open the port!")print("Press any key to terminate...")msvcrt.getch()quit()

First, controller opens #port_num1 and #port_num2 port to do serial communication with the Dynamixel. If it fails to open the port, the example will be terminated.

# Set port1 baudrateifdynamixel.setBaudRate(port_num1,BAUDRATE):print("Succeeded to change the baudrate!")else:print("Failed to change the baudrate!")print("Press any key to terminate...")msvcrt.getch()quit()# Set port2 baudrateifdynamixel.setBaudRate(port_num2,BAUDRATE):print("Succeeded to change the baudrate!")else:print("Failed to change the baudrate!")print("Press any key to terminate...")msvcrt.getch()quit()

Secondly, the controller sets the communication BAUDRATE at #port_num1 and #port_num2 port opened previously.

As mentioned in the document, above code enables each Dynamixel`s torque to set their status as being ready to move.

write1ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num1 and #port_num2 ports, writing 1 byte of TORQUE_ENABLE value to ADDR_MX_TORQUE_ENABLE address. The function checks Tx/Rx result and receives Hardware error.
getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

During while loop, the controller writes and reads each Dynamixel position through packet transmission/reception(Tx/Rx).

To continue their rotation, press any key except ESC.

write2ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num1 and #port_num2 ports, writing 2 byte of dxl_goal_position[index] value to ADDR_MX_GOAL_POSITION address. The function checks Tx/Rx result and receives Hardware error.
getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

read2ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num1 and #port_num2 ports, requesting 2 bytes of value in ADDR_MX_PRESENT_POSITION address. The function checks Tx/Rx result and receives Hardware error.
getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

Reading their present position will be ended when absolute value of (dxl1_goal_position[index] - dxl1_present_position) or (dxl2_goal_position[index] - dxl2_present_position) becomes smaller then DXL_MOVING_STATUS_THRESHOLD.

At last, it changes their direction to the counter-wise and waits for extra key input.

write1ByteTxRx() function orders to the #DXL1_ID and #DXL2_ID Dynamixels in PROTOCOL_VERSION communication protocol through #port_num1 and #port_num2 ports, writing 1 byte of TORQUE_DISABLE value to ADDR_MX_TORQUE_ENABLE address. The function checks Tx/Rx result and receives Hardware error.
getLastTxRxResult() function and getLastRxPacketError() function get either, and then printTxRxResult() function and printRxPacketError() function show results on the console window if any communication error or Hardware error has been occurred.

# Close portdynamixel.closePort(port_num1)dynamixel.closePort(port_num2)